The present invention relates to an optical detector assembly, and more particularly to an optical detector assembly for detecting concentration of dust, smoke or the like contained in the flow of air passing therethrough.
In an optical detector assembly of this kind, optical elements such as a light emission element, a light receiving element and lens will suffer in their functions from dust adhered thereto. Particularly, in adaptation of the optical detector assembly to an automobile, there will occur an error in detection due to presence of alien particles such as dirt, water, snow and the like in the flow of dust to be detected by the optical elements. It is also apparent that if such alien particles adhere to the optical elements, the function of the detector assembly will suffer severely. Furthermore, there will occur an error in detection due to presence of an external disturbance light entering into the light receiving element of the detector assembly.